1. Field of the Invention
The present invention relates to a functional polymer membrane and a method for producing the same.
2. Description of the Related Art
Regarding membranes having various functions as functional polymer membranes, known examples include an ion-exchange membrane, a reverse osmosis membrane, a forward osmosis membrane, and a gas separation membrane.
For example, an ion-exchange membrane is used for electrodeionization (EDI), continuous electrodeionization (CEDI), electrodialysis (ED), electrodialysis reversal (EDR), and reverse electrodialysis (RED).
Electrodeionization (EDI) is a water treatment process, by which ions are eliminated from an aqueous liquid by using a thin film and utilizing potential in order to achieve ion transport. Unlike other water purification technologies such as conventional ion exchange, electrodeionization can be used to produce ultrapure water without requiring the use of chemical agents such as acids or caustic soda. Electrodialysis (ED) and electrodialysis reversal (EDR) are electrochemical separation processes by which ions and the like are eliminated from water and other fluids.
When a functional polymer membrane (hereinafter, also simply referred to as “membrane”) is used for EDI, CEDI, ED, EDR and the like, it is preferable that the membrane has low electrical resistance and a low coefficient of water permeability. On the other hand, a functional polymer membrane is subjected to stress during integration into a treatment apparatus. Also, the dimensions of a functional polymer membrane should not change significantly during a treatment. Therefore, a functional polymer membrane is required to have certain mechanical strength, and for example, a functional polymer membrane may be imparted with mechanical strength by using a support having a predetermined thickness. For example, JP2013-503038A describes an ion-exchange membrane for electrodialysis having a microporous membrane support having a thickness of more than about 20 μm and less than 155 μm.